1. Technical Field
The present invention is related to a process for manipulating microscopic, dielectric particles as well as a device therefor.
In order to examine microscopic particles, such as biological cells, synthetic particles or large molecules, such as proteins, these particles need to be separated, moved at the site of examination, focussed and retained there. The particles need to be moved singlely or in groups in prescribed different directions.
For three-dimensional microscopy and for spectroscopic procedures, the particles have to be maintained in defined positions without contact while simultaneously maintaining manipulatability, i.e., by way of illustration, rotation about defined angles and axes.
Focussing should occur, depending on the case of application, in a point-shaped, linear or areal manner.
2. State of the Art
A known process for manipulating small dielectric particles is dielectrophoresis. In this way, the particles are subject to an inhomogeneous, electric field which polarizes the particles unsymmetrically. The particles are moved in the direction of the higher, resp. lower field strength and collect at the respective electrode. Mixtures of different types of particles can be separated with alternating electric fields.
Restrictions in the utilization of this known process result from the particles always being moved, independent of the direction of the field, to the site of high, resp. low field strength. With a prescribed configuration, movement of particles is thus only possible in one direction. There is a concentration of particles at the electrode so that the particles cannot be retained in free space.
In the state of the art processes, the electric field usually has curved field lines. As the particles move along the field lines, straight transport over longer stretches, by way of illustration, in channels of microstructures, is not possible.
In a process from a different generic type, notably a process for differentiating particles in a medium, there is already known from DE 33 25 843 C2, to suspend the particles in a fluid and expose them to a changing electric field. Of particular interest, the teaching of the DE 33 25 843 C2 FIG. 1 concerning a generator/amplifier arrangement for generating a commonly known plurality of alternating voltages having differing phases, is applicable for use as a generator/amplifier with the present invention. The application of this process for manipulating microscopic, dielectric particles has, however, hitherto not been considered.